On Wed, Jan 13, 2021, at 4:06 PM, Philippe Mathieu-Daudé wrote:
> On 1/13/21 3:15 AM, Jiaxun Yang wrote:
> > 在 2021/1/13 上午5:54, Philippe Mathieu-Daudé 写道:
> >> Loongson is next step in the "MIPS decodetree conversion" epic.
> >> Start with the simplest extension.
> >>
> >> The diffstat addition comes from the TCG functions expanded.
> >> The code is easier to review now.
> >> IMO this is also a good template to show how easy a decodetree
> >> conversion can be (and how nice the .decode file is to review) :P
> >>
> >> Please review,
> >>
> >> Phil.
> >>
> >> Based-on: <20210112184156.2014305-1-f4...@amsat.org>
> >> "decodetree: Allow 'dot' in opcode names"
> >>
> >> Philippe Mathieu-Daudé (6):
> >> target/mips: Re-introduce OPC_ADDUH_QB_DSP and OPC_MUL_PH_DSP
> >> target/mips: Convert Loongson DDIV.G opcodes to decodetree
> >> target/mips: Convert Loongson DIV.G opcodes to decodetree
> >> target/mips: Convert Loongson [D]DIVU.G opcodes to decodetree
> >> target/mips: Convert Loongson [D]MOD[U].G opcodes to decodetree
> >> target/mips: Convert Loongson [D]MULT[U].G opcodes to decodetree
> >>
> >> target/mips/translate.h | 1 +
> >> target/mips/godson2.decode | 29 +++
> >> target/mips/loong-ext.decode | 30 +++
> >
> > Hi Philippe,
> >
> > Thanks for the template!
> >
> > Just a small question, where should we perform ISA availability check?
> > Before calling generated decoder or after decoded?
>
> The check is done before in decode_loongson:
>
> bool decode_loongson(DisasContext *ctx, uint32_t insn)
> {
> if ((ctx->insn_flags & INSN_LOONGSON2E)
> // if ISA available ...
> && decode_godson2(ctx, ctx->opcode)) {
> // and opcode supported
> // return success
> return true;
> }
> // else keep going ...
>
> if ((ctx->insn_flags & ASE_LEXT)
> && decode_loong_ext(ctx, ctx->opcode)) {
> return true;
> }
>
> // finally return false, if nothing else decoded
> // gen_reserved_instruction will be called in the
> // main decode loop.
> return false;
> }
>
> >
> > Loong-EXT is a super set of Loongson2F's Godson2 and MMI instructions,
> > how could we tell it?
>
> MMI instructions are currently handled by the ASE_LMMI flag,
> a different decoder (which will also be handled by this function,
> similarly to ASE_LEXT).
SWC2/LWC2/SDC2/LDC2 family of LEXT instructions do exist on LEXT but not
Loongson-2F.
Thanks.
>
> Regards,
>
> Phil.
>
--
- Jiaxun
